looked at doing a backpacking trip in Yosemite last year, but couldn't squeeze enough time away from home. All of my backpacking has been back east. Looking this year at a HST trip, and am concerned about snow and/or water. My hiking buddy is not available until mid September. Any major concerns at that time?

I'm an REI guide and was worried how my beginning bkpk clients would respond to the weather so I packed the big tarp. It worked out great to sort food under, etc. My clients were good sports with great attitudes.

The weather is the wonderful in September (usually) but be prepared. The smaller streams will have dried up but the major ones will still be flowing and the lakes will still have water in them. Lovely, all in all :-)

September should be fine. Less people, no skeeterz and
pretty stable weather in the first half of the month are the pluses.
No flowers, dried out creeks, shorter and cooler days especially
second half of the month are the minuses for some, but to me any
month spent in the Sierra is a plus.

I was also caught in the September snow but it was more of a suprise than anything else. Normally snow at that time of year will last about 2 days, this one was about 4 days. However, I use a tarp and bivy system for sleeping and I stayed dry and warm.

One of the big draws for me to backpack after mid-September is the fishing. Fall flyfishing in the Sierras is pure magic. Even in very poor weather Fall fishing is magic.

Maverick's a good summary. Even winter in the Sierra is relatively mellow compared to mountains east of the Sierra. The usual hiking season in the Sierra covers most of June through October with the end of the season getting more and more chancy for yuck weather. In May there is left over snow at the higher altitudes (above 10,500) and in November you can expect new snow of some depths. There have been the 'rogue' snow dumps in mid June of over 4' as well as big ones in September/October. Above 11,000 you can expect snow or winter conditions on any day of the year.

Many consider the best time of year overall is last week in July through mid August. There is still a considerable run off on creek crossings but just enough to make each an adventure and at times a challenge but not so dangerous as to be fool hardy (on the HST). With this run off there are lots of flowers at all altitudes. There are a few places where mosquitoes are a hazard, but can be managed if you camp with that problem in mind. The weather is warm to hot in the daytime and cool (frost any time of the year above 10,000') at night. A 20F sleeping bag will spend much of its time under you. Snow is still on the ground on most of the passes, but easily hiked. Daylight will only get shorter.

As you go later than August, it gets cooler in daytime and night. Expect clothing for the unexpected 20F's in August as well as September. By end of August you have lost most of the afternoon thundershowers, the flowers, and the mosquitoes except near large water. Your temperatures in the daytime seldom get into the 90's as they did in August.

By September you are well into fall. There is no shortage of water, but it is farther in between than the month earlier. Most of the winter run off has occurred. Most grasses are starting to brown, no flowers but the hearty, chances of nasty, cold weather increase starting toward the end of September with snow covering very possible in late October. The snow won't 'stick' yet, however. Most weather is well forecasted except for some unusual local abnormalities caused by the high mountains. School is in session. Parents have to be home too. Others on the trails with you come at less and less frequent intervals. The popular trails are tapering off some. Great month for star gazing.

October is still a good month but even the hearty need to keep an eye on the barometer and pack an extra woolly jumper for cool nights and mornings.

That trip should be a good for weather. Enjoy it. Beautiful walk...take your time especially inhaling the scenery as you leave Bearpaw and the upper end of the Arroyo (9 Lakes Basin) on the other side. I think the high trail above Moraine Lake a better route for scenery. Even a layover at the Arroyo and dayhike to Little Five Lakes would be a teaser. Consider the upper reaches of the Kern drainage as a possible side or additional jaunt of an extra day or so. Well worth the added effort since you worked almost 5 days or so to get there.

Just a warning. Many eastern hikers are amazed that there are times when hiking in the Sierra a trail is uphill for more than a day. Even a half day uphill is a surprise. So plan on it from a fitness standpoint.